In general, general-purpose spectrophotometers have light sources, spectrometers, specimen chambers, detectors, signal amplifiers, controllers and the like built into the spectrophotometer unit. Optical components such as holders for holding specimens in the optical path over which a measuring light beam passes are mounted in a specimen chamber such that they can be mounted or removed. The specimen is placed in the optical path using these components, the measuring light beam is radiated in the wavelength range suited to the measurement purpose, transmitted light is guided to a detector where it is detected as a detection signal (electrical signal), signal processing and operations such as amplification and A/D conversion are conducted, and transmittance and absorbance are calculated. Measurement results can then be obtained by displaying measurement data such as transmittance and absorbance on a monitor screen.
In recent spectrophotometers, a variety of accessories that can be optionally mounted and removed has been provided to match the specimen size, shape, number, measurement purpose, measurement method, and the like. By selecting these accessories as needed and mounting them in the spectrophotometer unit, the desired measurements can be accurately and easily performed.
When mounting accessories in the spectrophotometer unit and conducting measurements, measuring without being aware that these accessories have been mounted may lead to mistakes in input settings and operation of the spectrophotometer, and cause mistaken measurement data to be output.
For that reason, the installation of accessory recognition mechanisms such as electrical contacts for recognizing accessories at specific locations on accessories and corresponding specific locations on the spectrophotometer unit has been disclosed (Patent Literature 1).
Spectrophotometers have also been disclosed wherein the accessories themselves have IC chips (ID tags) that store information about the accessory and identify their configuration. When the accessory is mounted in the specimen chamber, the accessory information is read by a reading means installed in the specimen chamber of the spectrophotometer unit and the information is sent to a control computer (Patent Literature 1 and 2).
The devices described in the Patent Literature mentioned above use the same detector built into the spectrophotometer unit regardless of whether accessories are installed or not. Accordingly, measurement is conducted by built-in detectors at settings that correspond to either accessories being mounted or not being mounted, using the accessory recognition mechanisms of the spectrophotometer unit to recognize whether or not an accessory is currently present.
As it happens, integrating spheres may be used as accessories, for example, when measuring diffuse reflectance of specimen surfaces. Since integrating spheres must be placed close to detectors, measurements are conducted using an external detector and not using the built-in detector.
When an accessory having an external detector is mounted in the main unit of a spectrophotometer, measurements are conducting using either the built-in detector or the external detector.
FIG. 5 is a schematic that shows one example of an external accessory of this type mounted in the specimen chamber of spectrophotometer M. FIG. 6 is a schematic that shows the state where no external accessory is mounted in spectrophotometer M (when measuring transmittance). Note that while actual measuring light beams often use a double beam of signal light beam and reference light beam, only the signal light beam is explained here, and the reference light beam is not explained here.
Spectrophotometer M comprises main unit 10, personal computer 11, which primarily conducts input and output necessary for measurement, and external accessory 12.
Main unit 10 is equipped with light source 21, spectrometer 22, specimen chamber 23, detector 24 (built-in detector), signal amplifier 25, A/D converter 26, controller 27 (firmware), wavelength stepping mechanism 22a of spectrometer 22, and a gain setting mechanism 29 for signal amplifier 25.
The light emitted from light source 21 (for example, a deuterium lamp) is divided into monochromatic light by spectrometer 22 using a diffraction grating and is guided through an input window disposed on the wall of specimen chamber 23 into the specimen chamber. Light source 21 adjusts the direction of the optical path using light source mirror 21a to send light into spectrometer 22. Spectrometer 22 uses wavelength stepping mechanism 22a, which adjusts the angle of the diffraction grating, to adjust the wavelength of the monochromatic light sent to specimen chamber 23.
Specimen chamber 23 is provided with an optical path switching mirror 23a (optical path switcher) at location P on the optical path that bends the direction of travel of the light to guide the light to external accessory 12. Location P can be positioned anywhere on the optical path, but in almost all devices, it is positioned where optical path switching mirror 23a can replace cell holder 23b for transmission measurement is installed for use during ordinary transmission measurement when no external accessory 12 is mounted (FIG. 6). A positioning part for mounting is formed on the bottom surface at the position where cell holder 23b is mounted, making it easy to be mounted.
Since the measurement optics switch after specimen chamber 23, the device configuration for ordinary transmission measurement is explained first. As shown in FIG. 6, light that travels straight through cell holder 23b at position P is emitted through an exit window disposed on the wall of specimen chamber 23, is guided to detector 24 (the built-in detector), and a detection signal is output.
The signal output from detector 24 is amplified by signal amplifier 25, whose amplification factor is adjusted to a desired factor by gain setting mechanism 29, and is sent via A/D converter 26 to controller 27 as a measurement data signal (digital data).
Some detectors, such as photomultiplier tubes, use a gain setting mechanism to adjust the amplification factor by controlling the negative high voltage of the photomultiplier tube.
Controller 27 is a so-called “firmware” that stores information such as programs and parameter settings required for control and controls the entire unit. The controller 27 also performs data processing on the measurement data that it receives and calculates transmittance, absorbance and the like.
Personal computer 11 displays the transmittance and absorbance measurement data calculated by controller 27 on a monitor screen in a prescribed format as the output data.
To be described next is the device configuration with external accessory 12 mounted in specimen chamber 23 of the spectrophotometer.
As shown in FIG. 5, light reflected by optical path switching mirror 23a (optical path switcher) disposed at position P is guided through incident window 31a of integrating sphere 31, which is an optical device of external accessory 12, and is output as a detection signal from detector 32 (external detector) installed in the wall of integrating sphere 31. The specimen is mounted in accessory 12.
The output signal from detector 32 is amplified using a desired amplification factor by signal amplifier 25 via external cable 33, connector 34, and internal cable 35, and is sent through A/D converter 26 to controller 27 as measurement data signal (digital data). Controller 27 also performs data processing on the measurement data signal and calculates transmittance, absorbance and the like. Output data for transmittance, absorbance and the like is displayed on the monitor screen of personal computer 11.